All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Permanent facial paralysis is a difficult challenge for patients and physicians, as it creates both substantial functional and psychological problems for the patient. Unfortunately, facial paralysis is not an uncommon problem: the annual incidence has been estimated to be approximately 70 cases per 100,000. An estimated 127,000 new cases of permanent facial paralysis are diagnosed annually in the United States alone.
Current treatment involves free tissue microvascular transfer of an isolated muscle to the face and connecting its nerve to a motor nerve in the head and neck area (e.g., masseter or hypoglossal nerve, or nerve graft originating from the contralateral and functional facial nerve). This surgery, along with other dynamic facial reanimation surgeries, is currently performed in a small number of tertiary care centers around the world. The surgeries are lengthy and at times multi-staged, involve at least two vascular and one neural microanastamoses, only provide some semblance of a smile, and do not address the eye. Accordingly, these procedures (1) may not be optimal or offered to patients with substantial co-morbidities who may not tolerate one or more 6 to 12 hour surgeries under general anesthesia, (2) require head and neck surgeons with highly-specialized training and expert familiarity with surgical anatomy outside the head and neck, and (3) typically only provide patients with, on average, eight millimeters (˜⅓ of an inch) of oral commissure excursion in a non-spontaneous fashion (Hadlock et al., 2011). Patients and families often have to travel hundreds if not thousands of miles to be treated at one of very few facial nerve centers in the United States and internationally. These personal expenditures, along with the tremendous health care costs of the surgeries, several days of intensive care unit admission for free tissue graft monitoring, and work intensive postoperative care and physical therapy, can be quite substantial. Moreover, because the nerve in the head and neck has to slowly grow into the nerve and muscle of the free graft, results are not immediate and take ˜6 to 18 months to emerge. Finally, in about 10% of the patients, the free gracilis muscle does not survive. These patients need to return to operating room under general anesthesia to remove the necrotic muscle graft and be left as they were before the initial surgery, only now with a large facial scar.
Another currently available option involves introducing non-muscular material to the face with the goal of improving facial symmetry and oral or blink function. For example, connective tissue from the thigh can be harvested and transferred to the face to pull the corner of the mouth superiorly or to dilate a collapsed nasal valve. Moreover, an inert metal weight can be inserted into the upper eyelid to passively assist in eye closure. These interventions are intended only to moderately improve function and provide no dynamic movement to the paralyzed side of the face. In summary, the results of these invasive surgeries, when compared to the resting and dynamic states of the face prior to the onset of facial paralysis, are frequently suboptimal.
Thus there is a need in the art for novel and more effective treatments for muscle and nerve damage, including facial paralysis.